Electrical module

ABSTRACT

An optical encoder module includes a housing that includes at least one recess having an open end and an opposite closed end, and an electrical component accommodated within the recess. A first locking member is formed on the electrical component and a second locking member is formed in the housing. The first and second locking members are engaged with each other for locking the electrical component, when inserted into said recess, into a locking position. At least one resiliently compressible protrusion is provided between the electrical component and the closed end of the recess so as to be resiliently compressed therebetween into its compressed state when the electrical component is locked in the recess in its locking position.

FIELD OF THE INVENTION

The present invention relates to an optical encoder, especially to anoptical encoder module having an optical emitter and an optical detectorspaced apart from each other, but aligned to and interlocked withrespect to each other within a housing.

BACKGROUND OF THE INVENTION

In an optical encoder module, the emitter and the detector have to bespaced apart from each other and aligned to each other such that, forexample, a code card or a code wheel drawn or rotated, respectively, ina gap between the emitter and the detector can be detected and read bythe encoder. Light emitted by the emitter is either blocked or passed bythe code card or wheel and then detected by the detector. Therefore, itis important that the emitter and the detector are exactly aligned toeach other, i.e. the emitter and the detector have to accurately overlapeach other.

U.S. Design Pat. No. 329,193 discloses an optical encoder module havingan optical emitter and an optical detector, the emitter and the detectorbeing each provided with a solid molded housing, wherein both theemitter and detector housings are held together by means of a bracket.The bracket has a locking plate including a locking opening. The opticalencoder module (i.e. one of the housings) has a locking protrusion thatengages with the locking opening of the locking plate. Ribs are formedinside the bracket, and the emitter and detector housings are providedwith laterally elongated grooves for receiving the ribs of the bracket.

However, since the emitter and detector housings can be manufacturedwith certain tolerance values and therefore with some accuracy only,once the respective housings are held together with the bracket, theemitter and the detector can be offset relative to each other resultingin deterioration of the detecting operation. This problem can further bedeteriorated by mechanical inaccuracy of the bracket and an inaccurateengagement of the ribs of the bracket with the elongated grooves in theemitter and detector housings.

Other known arrangements do not mold the emitter and detector componentsin respective housings. In this case, the emitter and detectorcomponents are only provided with a simple encapsulation and aremechanically inserted into separately manufactured housings.

Inserting components inside a housing is a well-known operation in manyassembly processes. In many cases, the components need to be fittedtightly and snugly inside the housing such that they maintain theirpositional orientations vital to the functioning of the completelymounted assembly. However, the dimensions of the components as well asthe housings are subject to fabrication tolerances that cause thecomponents to have slightly different dimensions. Because of thesedimensional variations, matching problems may arise when the componentsand the housing or housings are mounted into an assembly.

In the assembly process where components are being inserted intorespective recesses of a housing, it is important that the tolerances ofboth the components and the recesses are compatible. For perfectmatching, the dimensions of, e.g the length of the recess should beequal to the dimensions, e.g. the length of the component. However,there are tolerances in both of these dimensions. When the length of thecomponent is at maximum dimension and the length of the recess is atminimum dimension, it may even happen that the component cannot beinserted into the housing. Conversely, when the length of the componentis at minimum dimension and the length of the recess is at maximumdimension, the component will be too loose after insertion into thehousing.

In order to ensure that all components be inserted into the housing, thetolerances are typically specified such that the maximum dimension ofthe component is equal to the minimum dimension of the respective recessin the housing. In this case, a mismatch of the component and thehousing is prevented.

Furthermore, in order to ensure an accurate positional orientation ofthe component in the respective housing, generally glue, adhesive, aclip or a plug is used to secure the component in the housing. In othercases, after insertion of the electrical component into the housing, thehousing is deformed through heat staking such that the component isjammed tight inside the housing. In other instances, a mechanical catchor latch is used. Yet in other cases, the component is sized such thatthere is mechanical interference between the component and thecorresponding recess during the component insertion process.

Such methods are successflly used in the industry but they suffer fromlimitations. Glue, adhesive, plugs or clips represent additionalmaterials that naturally incur extra costs. In addition, an extraprocess step is needed to handle these materials prior to or aftercomponent insertion. This makes the assembly process more complicatedand increases the cost of manufacturing. In some cases mechanicalcatches or latches cannot be applied because it is very difficult oreven impossible to make them, and mechanical interference can lead todeformation of the housing, and thereby to the formation of cracks inthe housing and/or the components.

SUMMARY OF THE INVENTION

One feature of the present invention is to provide an optical encodermodule in which components are tightly fitted inside a housing afterinsertion of the components into the housing.

Another feature of the present invention is to provide an opticalencoder module in which components are tightly fitted inside a housingafter insertion of the components into the housing, and the differencesin the dimensions of the components and that of the housing due tovariations in the respective manufacturing processes are securelycompensated for.

A further feature of the present invention is to simplify the assemblyprocess of an optical encoder module with an emitter and a detectorspaced apart such that the overall manufacturing costs are reduced.

In accordance with one embodiment of the present invention, an opticalencoder module includes a housing that includes at least one recesshaving an open end and an opposite closed end, and an electricalcomponent (e.g., an emitter or a detector) accommodated within therecess. A first locking member is formed on the electrical component anda second locking member is formed in the housing. The first and secondlocking members are engaged with each other for locking the electricalcomponent, when inserted into said recess, into a locking position. Atleast one resiliently compressible protrusion is provided between theelectrical component and the closed end of the recess so as to beresiliently compressed therebetween into its compressed state when theelectrical component is locked in the recess in its locking position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an optical encoder moduleaccording to an embodiment of the present invention, shown in a statebefore locking the electrical components.

FIG. 2 is a perspective cross-sectional view of the optical encodermodule of FIG. 1.

FIG. 3 is a schematic cross-sectional view of the optical encoder moduleof FIG. 1, wherein the electrical components are in their respectivelocking positions.

FIGS. 4 and 5 are perspective cross-sectional views of the opticalencoder module of FIG. 3, and

FIG. 6 a shows a schematic plan view of an electrical componentaccording to a further preferred embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIGS. 1-6, an optical encoder module is shown thatimplements one embodiment of the present invention. As will be describedin more detail below and in accordance with one embodiment of thepresent invention, the optical encoder module includes a housing 1 whichhas two recesses 2, 3 arranged one above the other. Each recess 2, 3 hasan open end and closed end opposite to the open end, the closed endbeing formed by a boundary wall 4. Two locking openings 5 are formed inopposite sides of the housing 1 in overlapping relationship with thecorresponding recesses 2-3. A gap 6 is formed in the housing 1 betweenthe recesses 2-3 such that it is open to one end of the housing 1 beingadjacent to the closed end of the recesses 2-3. Each recess 2, 3 isprovided with two resiliently-compressible protrusions 7 protruding intothe recesses 2-3, being integrally formed with the housing 1, andarranged spaced apart from each other on the boundary wall 4 of therecesses 2-3. An encapsulated optical emitter 8 is accommodated withinthe one recess 2, and an encapsulated optical detector 9 is accommodatedwithin the other recess 3. Each of the encapsulation of the emitter 8and that of the detector 9 has a locking projection 10 for engaging withthe respective locking openings 5 to lock the emitter 8 and the detector9 into a locking position in the respective one of the recesses 2-3.

The resiliently-compressible protrusion 7 allows for tight and snugfitting of the emitter 8 and the detector 9 within each of the recesses2-3 after locking the respective component (i.e., the emitter 8 or thedetector 9) by the first and second locking members or projections 10without the use of any additional adhesive, glue, clip, plug or anotherattachment means or method. The arrangement and the design of thecompressible protrusion 7 enable the optical encoder module toaccommodate the dimensional tolerance of either the emitter 8 or thedetector 9 and each of the recesses 2-3 during assembly. The arrangementand the design of the compressible protrusion 7 also cause theprotrusion 7 to be able to consistently maintain the component (i.e.,either the emitter 8 or the detector 9) in a tight fit within thehousing 1. The resilience of the compressible protrusion 7 enables asufficient flexibility such that the compressible protrusion 7 can becompressed to collapse to accommodate the slack due to the effect oftolerance.

If the compressible protrusion 7 is resiliently compressed into itscompressed state, it will be surface forced and deformed. Therefore, theheight of the protrusion 7 must be such that it is still compressed inthe case of a tolerance where there is a maximum gap between thecomponent (i.e., either the emitter 8 or the detector 9) and the closedend of each of the recesses 2-3, i.e., the height of the compressibleprotrusion must be larger than the maximum gap formed between the closedend of the respective one of the recesses 2-3 and the electricalcomponent (i.e., either the emitter 8 or the detector 9) in the lockingposition of the electrical component. On the other hand, the protrusion7 must be designed with regard to its compressibility such that in thecase of minimum gap it can be compressed to a minimum height being equalto the width of the gap. In this latter case, the protrusion 7 is fullycompressed. Practically, a small gap is desirous to accommodate thecompressed protrusion 7 and, therefore, the length of each of therecesses 2-3 and that of the electrical component (i.e., either theemitter 8 or the detector 9) with the respective tolerance ranges shouldbe dimensioned accordingly.

By forming the resiliently compressible protrusion 7 between theelectrical component (i.e., either the emitter 8 or the detector 9) andthe closed end of each of the recesses 2-3, the differences indimensions of the components 8-9 and the recesses 2-3 due to variationsin fabrication are securely compensated for, so that an exact andconsistent positioning and locking of the components 8-9 in the housing1 of the optical encoder module is achieved.

The compressible protrusion 7 is integrally formed on the closed end ofthe respective recess (i.e., 2 or 3) facing the electrical component(i.e., either the emitter 8 or the detector 9). This allows for a simpleproduction of the housing together with the compressible protrusion withlow manufacturing costs. Furthermore, by integrally forming thecompressible protrusion at the closed end of the recess, the protrusionhas an exactly predetermined position in relation to the bottom end ofthe electrical component facing the closed end of the recess so thatinaccuracies in positioning the compressible protrusion by separatelyattaching the protrusion to the closed end of the recess are avoided. Inthis embodiment the housing and the compressible protrusion can beformed from the same material, and a variety of standard components canbe accommodated and locked in the recess of the housing. Alternatively,each of the compressible protrusions 7 is integrally formed on thebottom end of the respective electrical component facing the closed endof the respective recess.

According to one embodiment of the invention, each of the compressibleprotrusions 7 is formed in a tapered shape or as a semicircular dome inorder to facilitate the collapsing effect and to ensure that there isadequate space to accommodate the collapsing material. More generally,each of the compressible protrusions 7 is shaped such that it has asmaller dimension at its end facing to the bottom end of the componentand being engaged in surface contact with the component. Thisfacilitates the compression of the protrusion so that the inserting andlocking operation of the component into the recess can be easilyperformed with low force using the resilience characteristic of theprotrusion material.

Alternatively, each of the compressible protrusions 7 can be formed in alinearly elongated shape. In this case, when inserting the respectivecomponent (i.e., the emitter 8 or the detector 9) into the respectiverecess, the bottom end surface of the component is contacted by thelinearly elongated compressible protrusion so that a uniform abutting ofthe component against the protrusion is ensured and the pressure actingon the bottom end of the component is uniformly distributed.

According to an embodiment of the invention, two compressibleprotrusions are provided side by side on the closed end of the recess.In this case, it is achieved that the bottom end of the component isuniformly aligned to the closed end of the recess of the housing toconsistently maintain the component in a tight fit. The two compressibleprotrusions ensure that the component is properly seated.

To achieve proper deformation characteristics, the compressibleprotrusion 7 can be made of plastic or a malleable metal. Such materialsare soft in nature and sufficiently meet the requirements regardingcompression characteristics of the protrusion.

The housing 1 is integrally made of, for example, a plastic material. Inaddition, each of the recesses 2 and 3 has a substantially rectangularcross-sectional shape. The locking openings 5 are formed in oppositesides of the housing 1 in overlapping relationship with thecorresponding recesses 2, 3. Preferably, the housing 1 and thecompressible protrusion 7 formed on the closed end of the recess aremade of a softer material than that of the electrical component (i.e.,the emitter 8 or the detector 9) so that the compressible protrusion 7is reliably compressed into its compressed state. In this way it isensured that the compressible protrusion 7 made from softer material cancollapse against the harder material of the electrical component.Therefore, deviations in the locking position of the electricalcomponent are avoided which could otherwise occur due to deformations ofthe bottom end portion of the component that presses against thecompressible protrusion. Alternatively, if the electrical component hasthe compressible protrusions then the housing should be made from aharder material than that of the protrusions and the electricalcomponent.

The encapsulation of the emitter 8 and the detector 9 is made of amaterial that is harder than the plastic material of the compressibleprotrusion 7 integrally formed with the housing 1. Next, the lockingoperation of the emitter 8 and the detector 9 into the recesses 2, 3 isdescribed.

FIGS. 1 and 2 show the optical encoder module in a state before lockingthe emitter 8 and the detector 9. The emitter 8 and the detector 9 areinserted into the recesses 2, 3 of the housing 1 from the open end ofthe recesses 2, 3 in a direction toward the boundary wall 4 of therecesses 2, 3 until the compressible protrusions 7 formed at theboundary wall 4 are reached. Then, the bottom end of the emitter 8 andthe detector 9 is pressed against the compressible protrusions 7 untilthe locking projection 10 of the emitter 8 and the detector 9 is engagedwith the corresponding locking opening 5 in the housing 1.

FIGS. 3 to 5 show the optical encoder module in a locking position ofthe emitter 8 and the detector 9. In this position, the emitter 8 andthe detector 9 are completely locked in the recesses 2, 3 by engagingthe locking projections 10 with the locking openings 5 of the housing 1.The compressible protrusion 7 is resiliently compressed into itscompressed state between the bottom end of the emitter 8 and thedetector 9, respectively, and the corresponding boundary wall 4 of therecesses 2, 3. Therefore, the emitter 8 and the detector 9 are tightlyfitted in their locking position and accurately aligned to each other.

The emitter 8 and the detector 9 are spaced and aligned to each othersuch that a code card or wheel (not shown) drawn or rotated,respectively, through the gap 6 between the emitter 8 and the detector 9can he detected and read by the optical encoder module. The lightemitted by the emitter 8 is passed through or blocked by the code card(or code wheel) and then detected by the detector 9. Since the emitter 8and the detector 9 are exactly aligned to each other, i.e. the emitter 8and the detector 9 are arranged in an accurate overlapping position, areliable operation of the optical encoder module is ensured.

As schematically shown in FIG. 6, according to a further preferredembodiment of the invention, the encapsulation of the electricalcomponents (the emitter 8 and the detector 9) is further provided withtwo elongated triangle-shaped protrusions 11 on their opposite lateralsides. These protrusions 11 provide for a centering of the electricalcomponents in the recesses 2, 3 in lateral directions when theelectrical components are inserted in the respective recesses 2, 3, andthereby contribute to an even more accurate alignment of the electricalcomponents.

1. An optical encoder module, comprising: a housing which includes atleast one recess having an open end and an opposite closed end, thehousing further including a locking opening; an electrical component tobe accommodated within the recess, the electrical component including alocking member formed on a surface of the electrical component, whereinthe locking member and the locking opening are engaged with each otherfor locking the electrical component, when inserted into said recess,into a locking position, and wherein unlocking the electrical componentfrom the locking position enables removing and separating the electricalcomponent from the housing; and at least one resiliently compressibleprotrusion between the electrical component and the closed end of therecess so as to be resiliently compressed therebetween from itsuncompressed state into its compressed state when the electricalcomponent is inserted into the recess and locked therein in its lockingposition.
 2. The optical encoder module according to claim 1, whereinthe compressible protrusion is integrally formed at the closed end ofthe recess facing the electrical component.
 3. The optical encodermodule according to claim 1, wherein the compressible protrusion isintegrally formed on a bottom end of the electrical component facing theclosed end of the recess.
 4. The optical encoder module according toclaim 2, wherein the compressible protrusion is formed in a taperedshape or in the form of a semicircular dome.
 5. The optical encodermodule according to claim 3, wherein the compressible protrusion isformed in a tapered shape or in the form of a semicircular dome.
 6. Theoptical encoder module according to claim 2, wherein the compressibleprotrusion is formed in a linearly elongated shape.
 7. The opticalencoder module according to claim 3, wherein the compressible protrusionis formed in a linearly elongated shape.
 8. The optical encoder moduleaccording to claim 1, further comprising a second compressibleprotrusion that is provided side by side with the at least onecompressible protrusion.
 9. The optical encoder module according toclaim 2, wherein the housing and the compressible protrusion are made ofa softer material than that of the electrical component.
 10. The opticalencoder module according to claim 9, wherein the compressible protrusionis made of plastic or a malleable metal.
 11. The optical encoder moduleaccording to claim 1, wherein the housing further includes a secondrecess having an open end and an opposite end, wherein the recess andthe second recess are arranged vertically spaced apart and are parallelto each other, and wherein the electrical component is accomodatedwithin any one of the recess and the second recess.
 12. The opticalencoder module according to claim 1, wherein the electrical component isa light emitter of the optical encoder module.
 13. The optical encodermodule according to claim 1, wherein the electrical component is adetector of the optical encoder module.